33kV Insulator dust deposits

[martinrelayer]

Hi all,

We found dust spots (dust concentration) in the surface of an insulator (the trafo is under roof), and carbon spots also. I've attached a picture of the insulator there you can see the spots.

Is it possible that this can be internal cracking? (the trafo is 1st year in service) The tech havent found anything looking at it.

I've noticed the same phenomena in cast-resin trafos HV windings (33kV)

Any help will be much appreciated!!

Note: i'm not an experienced medium voltage tech...

regards,
Martín

 

[Zogzog]

Hard to tell from the picture, could have a corona issue there. Can you do a orona scan?

 

[martinrelayer]

I´m sorry, I misspelled, it's a bushing. I'm not so good in english...

Some guy from the mill said saw it sparking, then a tech cleaned it, and then no more sparks.

But anyone can tell something similar? It seems insulator damage to me but I'm not that experienced in HV.

thanks!!

 

[Zogzog]

Those "sparks" he saw probally looked like a purple force field around the bushing, it will come back, you need to replace that bushing when possible.

 

[martinrelayer]

What about dust spots/concentration?
I saw the same phenomena in the HV windings of cast-resin transformers

many thanks!

 

[NCTHAI]

From pictures difficult to predict but does not look like crack or something like that. These look like carbon deposits. You need to check for reasons. Inded there was sparking as said in the post.

Follow basic electrcial maintenance principles - keep it clean, cool, Dry and tight. And observe.

At first opportunity, lift and check for internal crack or sparking.

Regards,

NC

 

[prc]

Maximum electrical stress in bushing is at mounting area ie to earth.If you are no-longer seeing any sparking nothing to worry.If the area is prone to too much dust pollution,better to apply silicon grease ( eg RTV) on porcelains so that performace is not affected by pollution.

 

[Zogzog]

Colonite or Beaver butter are 2 products designed for this purpose.

 

[martinrelayer]

Great! Thanks a lot